This feature works like the select circle in any other modes. The user
can press "C" in preview or timeline and then select or deselect strips
by pressing the left or middle mouse button.
It’s an enhancement for the VSE preview because:
1. It makes it more similar to other editors in Blender
2. This behavior makes it easier to select specific overlapping strips
in preview, that is because the select circle only checks for the
origin of the strip.
Pull Request: https://projects.blender.org/blender/blender/pulls/141422
098be390ca